1. Field of the Invention
The present invention relates to a fuel cell formed by stacking electrolyte electrode assemblies and separators alternately in a stacking direction. Each of the electrolyte electrode assemblies includes a pair of electrodes and an electrolyte interposed between the electrodes. A reactant gas flow field for supplying a reactant gas is formed between the electrode electrolyte assembly and one of separators sandwiching the electrolyte electrode assembly in order to supply a reactant gas along a surface of the electrode. A coolant flow field is formed between adjacent separators, which are stacked together, for allowing a coolant to flow in a direction substantially perpendicular to the flow direction of the reactant gas.
2. Description of the Related Art
A polymer electrolyte fuel cell employs, for example, a membrane electrode assembly (MEA), which includes an anode, a cathode, and an electrolyte membrane (electrolyte) interposed between the anode and the cathode. The electrolyte membrane is a solid polymer ion exchange membrane. The membrane electrode assembly and separators sandwiching the membrane electrode assembly make up a unit of a power generation cell for generating electricity. Normally, a predetermined number of membrane electrode assemblies and separators are stacked together alternately to form a fuel cell stack.
In the power generation cell, a fuel gas flow field (reactant gas flow field) for supplying a fuel gas along the surface of the anode and an oxygen-containing gas flow field (reactant gas flow field) for supplying an oxygen-containing gas along the surface of the cathode are formed on a pair of separators sandwiching the membrane electrode assembly. Further, a coolant flow field for cooling power generation surfaces of the membrane electrode assembly is formed between adjacent separators which are stacked together.
For example, Japanese Laid-Open Patent Publication No. 2003-338300 proposes a fuel cell in which cooling is performed efficiently by supplying a coolant in a direction perpendicular to the flow direction of the reactant gases, i.e., the fuel gas and the oxygen-containing gas, whereby power generation can be performed efficiently.
As shown in FIG. 11, in the fuel cell, a first separator 1 and a second separator 2 are stacked together. The first separator 1 has a curved fuel gas flow field 3, and the second separator 2 has a straight oxygen-containing gas flow field 5 on a surface thereof facing a cathode 4.
The top surface of a straight portion 6 of the first separator 1 contacts the top surface of a ridge 7 of the second separator 2. The top surface of a curved portion 8 of the first separator 1 is spaced away from the top surface of the ridge 7. Thus, a coolant flow field 9 having the flow direction perpendicular to the flow direction of the oxygen-containing gas flow field 5 is formed between the first and second separators 1 and 2.